A case of an 8-year-old Japanese boy with a testicular large cell calcifying Sertoli cell tumor (LCCSCT) is presented. This report appears to be the first Japanese case of LCCSCT. The patient presented with left testicular swelling and gynecomastia. His family history was not contributory; however, his past history was remarkable for a benign myxoid tumor in the nasal cavity, which was removed at the age of 2 months. After removal of the testicular tumor, the gynecomastia disappeared gradually and no recurrence or metastasis developed during a 15 month follow-up period. Although the tumor was initially interpreted as a Leydig cell tumor, a review of the slides after the patient's past history of nasal myxoid tumor was revealed led us to the diagnosis of LCCSCT. An accurate diagnosis of LCCSCT is crucial because this tumor is occasionally associated with Carney complex, which can comprise various pathological conditions, including cardiac myxoma, that may be life-threatening. Myxoma of Carney complex has been described to occur in the heart, skin, oral cavity and breast in a wide age range, but there have been no reports referring to nasal myxoid tumor associated with Carney complex.